It has been previously proposed to provide audiometers in which the test frequency or test tones are controlled by sliders which are arranged at right angles with respect to each other. One of the sliders controls the frequency of the tone and the other slider controls the respective amplitude, or sound pressure level. Each pair of parameters--frequency and level--is indicated on the coordinate system, typically a Cartesian coordinate system by an illuminated dot. The abscissa represents frequency, and the ordinate the sound level. A diagramatic, or cross section paper can be placed on the indicator and the luminescent spots can be marked so that, at the end of a test, a complete audiogram is present. The luminescent dot is moved mechanically, or, in other words, a lightbulb which is illuminated each time at a test level and frequency is moved on the coordinate board. For precision in measurement, it is necessary that the coordinate or cross slide arrangement be, itself, a high precision structure.
A tone audiometer of this kind is described in the literature, see for example "Arzt und Wirtschaft", 1979, issue 9, pp 44 and 45. The apparatus there described is manufactured by the assignee of the present application.
It has also been proposed--see "Hearing Instruments", October 1977, p 41--that an oscilloscope be provided to indicate the respective coordinate points of the audiogram. The oscilloscope can be coupled to a plotter.